1. Field of the Invention
The present invention relates to an image forming apparatus, in which a cleaning blade is used to recover toner from an image bearing member, and more particularly, to a configuration structure of a cleaning auxiliary member which prevents excessive accumulation of toner on the cleaning blade.
2. Description of the Related Art
There is widely used an image forming apparatus in which a toner image formed on a photosensitive member is transferred, directly or through an intermediate transfer member, to a recording material to be thermally fixed. The image forming apparatus is provided with a cleaning device for recovering unnecessary toner from an image bearing member (a photosensitive member, an intermediate transfer member, a recording material conveying member, or a transfer roller) by using a cleaning blade.
In the cleaning device using the cleaning blade, when toner is excessively accumulated on the cleaning blade, the toner interferes with the operation of the cleaning blade, which impairs normal cleaning performance of the cleaning device. That is, an excessive pressure may be exerted on a distal edge of the cleaning blade, which may result in fusion bonding of the toner. And, the cleaning blade may be thermally deformed, which may result in slipping-out of the toner.
In recent years, along with the downsizing of the image forming apparatus, the cleaning device is reduced in capacity. On the other hand, the processing speed of image formation is becoming increasingly higher. As a result, when image formation with the use of a large amount of toner is successively performed, a toner accumulation rapidly builds up to be coagulated on the cleaning blade in a portion where the cleaning blade is rubbed against the image formable area of the image bearing member, which easily leads to the above-mentioned problems.
Japanese Patent Application Laid-Open No. 2008-224726 discloses a cleaning device in which the cleaning blade knocks off toner recovered from the photosensitive drum into a conveying screw so that the toner may be carried to a one end side of the photosensitive drum for recovery. The cleaning device includes an agitating member formed of a bent rod, which comes into contact with a conveying screw and intermittently vibrates, to thereby break down coagulated toner adhering to the conveying screw by the agitating member.
Japanese Patent Application Laid-Open No. 2003-248401 discloses a cleaning device which includes a wire tensioned along a distal edge of the cleaning blade. In the cleaning device, the wire vibrates in a longitudinal direction, with the result that toner coagulated on the distal edge of the cleaning blade is broken down and falls off.
In order to allow the cleaning blade to provide stable cleaning performance when the image forming apparatus is operated at a high processing speed, the cleaning blade may desirably have toner accumulated to an appropriate amount on the distal edge thereof so that a trace amount of toner may always be supplied to the rubbing portion. If no toner is supplied, the cleaning blade may generate a chatter vibration, or may be thermally deformed, which increases slipping-out of toner.
However, as illustrated in FIG. 5, in the image forming apparatus, a cleaning blade (91) needs to be disposed to extend outward beyond each of fly toner areas outside the image formable area of an image bearing member (51) for performing cleaning. Here, no toner image is formed outside the image formable area, and fly toner does not reach the outside of each of the fly toner areas. As a result, sufficient toner may not be supplied to the cleaning blade (91) in a part on an end thereof.
However, in practice, toner scraped off in the image formable area and in the fly toner areas flows along the distal edge of the cleaning blade (91) to diffusely move outward, with the result that toner is supplied all the way to the end of the cleaning blade (91).
As illustrated in FIG. 4A, toner accumulated on the cleaning blade (91) forms an accumulation distribution in which the toner accumulation amount reduces outward toward the end of the cleaning blade. Accordingly, toner flowing along the distal edge of the cleaning blade (91) side-slides outward in a manner of flattening the gradient of the accumulation distribution.
However, in a configuration including a cleaning auxiliary member (94) as illustrated in FIG. 4B, the cleaning auxiliary member (94) removes toner accumulated on the cleaning blade (91) too early, and the outward movement of toner along the distal edge of the cleaning blade (91) tends to become discontinuous. The cleaning auxiliary member (94) uniformly removes toner accumulated on the image formable area and on the fly toner areas, and hence the accumulation distribution for moving the toner outward toward the end of the cleaning blade (91) cannot be formed, which fails, as a result, a mechanism for causing toner flowing along the distal edge of the cleaning blade (91) to be driven by the gradient of the accumulation distribution to diffusely move outward.